Water-surfactant contact studied by 19F-1H heteronuclear overhauser effect spectroscopy.

Intermolecular 19F-1H cross-relaxation is measured using heteronuclear Overhauser effect NMR spectroscopy (HOESY) in the micellar solution of cesium pentadecafluorooctanoate. The results are analyzed in terms of a weak 1H-19F cross-relaxation between the water protons and the fluorines in the fluoroalkyl chain and a strong 19F-19F cross-relaxation within the fluoroalkyl chain. The water-surfactant cross-relaxation indicates a water approach to the first CF2 segment in the order of 2.0 A and a short (<<ns) water residence time. Evidence of fluorine hydration further inside the micelle is presented. Copyright 1998 Academic Press.